A second appeal to the High Court under Section 100 of the CPC has a very limited scope. It can only be entertained if it involves a "substantial question of law."
\[\begin{array}{rl} \bullet & \text{(A) This is the primary requirement; the High Court must formulate the substantial question of law.} \\ \bullet & \text{(B) The proviso to Section 100(5) gives the High Court the power to hear the appeal on any other substantial question of law not formulated by it, if it deems necessary.} \\ \bullet & \text{(C) The nature of the first appellate decree (whether contested or ex parte) does not bar a second appeal, as long as the decree involves a substantial question of law.} \\ \end{array}\]
Since all the above situations are covered under Section 100 and its procedure, "All of the above" is the correct answer.